Postcss received undefined instead of css string

Explanation:

The error message “postcss received undefined instead of css string” usually occurs when you try to pass an undefined value as the CSS string to the postcss function or plugin. This can happen due to various reasons, such as:

• Not importing or requiring the required stylesheet properly
• Using an incorrect identifier or variable name
• Not assigning a value to the CSS variable before passing it to postcss

To resolve this error, you need to ensure that you are passing a valid CSS string to the postcss function or plugin. Here are some examples that illustrate the possible causes and solutions:

Example 1: Incorrect Import or Require

Make sure you have properly imported or required the stylesheet before using it with postcss. For example:

    // Incorrect
    import postcss from 'postcss';
    import styles from './styles.css'; // Invalid import

    const processedStyles = postcss().process(styles); // Error: postcss received undefined instead of css string

    // Correct
    import postcss from 'postcss';
    import './styles.css'; // Correct import
  
    const processedStyles = postcss().process('.className { color: red; }'); // Correct CSS string
    
  

Example 2: Incorrect Identifier

Ensure that you are using the correct identifier or variable name when passing the CSS string to the postcss function. For example:

    // Incorrect
    import postcss from 'postcss';
    
    const css = '.className { color: red; }';
    const processedStyles = postcss().process(styles); // Error: postcss received undefined instead of css string

    // Correct
    import postcss from 'postcss';
    
    const css = '.className { color: red; }';
    const processedStyles = postcss().process(css); // Correct CSS string
    
  

Example 3: Unassigned CSS Variable

If you are passing a CSS variable to the postcss function, make sure it has been assigned a value before using it. For example:

    // Incorrect
    import postcss from 'postcss';

    let css;
    
    // Some logic to conditionally assign a value to css...
    
    const processedStyles = postcss().process(css); // Error: postcss received undefined instead of css string
    
    // Correct
    import postcss from 'postcss';

    let css;
    
    // Some logic to conditionally assign a value to css...
    
    css = '.className { color: red; }'; // Value assigned to css variable
    
    const processedStyles = postcss().process(css); // Correct CSS string
    
  

By reviewing your code and considering the above examples, you should be able to identify the cause of the error and fix it accordingly. Remember to ensure that you are passing a valid CSS string to the postcss function or plugin.